3G/4G wireless systems are characterized by high-speed downlink and uplink data services. In such systems, interference between different cells is an important issue. Fractional frequency reuse is a traditional (even though suboptimal) approach to multi-cell interference mitigation. For example, in a ⅓ fractional frequency reuse system, only ⅓ of the frequency band is allocated to each cell/sector. Static fractional frequency planning reduces interference and, hence, improves coverage at the price of reducing the total system throughput per unit of frequency resources (i.e., Hz), compared to the full frequency re-use scheme. In addition, frequency diversity and multi-cell diversity cannot be fully exploited.
Recently, base station (BS) coordination has emerged as a promising tool for inter-cell interference mitigation. If neighboring base stations can communicate through high-speed wireline links, they can jointly decide what power level each base station should choose on each frequency band in order to improve the network weighted sum-rate. Previous work in this area typically relies on centralized or semi-centralized optimization process. Some distributed schemes also exist for interference mitigation. However, one scheme can only be employed to maximize the total throughput and cannot be generalized to the weighted sum-rate case. Another process assumes that power is a continuous variable and requires the channel gain from all other BSs to the selected user in each BS, and thus requires more communication overhead. Yet another scheme employs simulated annealing to optimize the system throughput. While simulated annealing can guarantee the asymptotic optimality, it is at the price of infinitely-long convergence time. Other works have focused on distributed processes for fixed-bit-rate traffic that do not exploit multi-channel selectivity.